Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

- Add new ARM kernel option QEMU_WORKAROUNDS which can be
used in the code which needs to implement some specific
behaviour when being run under QEMU.
- Make PXA UART probe code to work under QEMU gumstix, which
doesn't emulate all the ports properly.

Support for the XScale PXA255 SoC as found on the Gumstix Basix and Connex
boards. This is enough to net-boot to multiuser.

Also supported is the SMSC LAN91C111 parts used on the netCF, netDUO and netMMC
add-on boards.

I'll be putting some instructions on how to boot this on the Gumstix boards
online soon.

This is still fairly rough and will be refined over time but I felt it was
better to get this out there where other people can help out.